diff --git a/tests/libtest/lib1521.c b/tests/libtest/lib1521.c
index 367680198..dee85a238 100644
--- a/tests/libtest/lib1521.c
+++ b/tests/libtest/lib1521.c
@@ -20,8 +20,8 @@
  *
  ***************************************************************************/
 #include "test.h"
-
 #include "memdebug.h"
+#include <limits.h>
 
 /* This source code is generated by mk-lib1521.pl ! */
 
@@ -29,8 +29,8 @@ struct data {
     char *blaha;
 };
 
-#define LO -2147483647
-#define HI 2147483648
+#define LO LONG_MIN
+#define HI LONG_MAX
 #define OFF_VAL (curl_off_t) 3123123123
 #define OFF_LO (curl_off_t) LO
 #define OFF_HI (curl_off_t) HI
diff --git a/tests/libtest/mk-lib1521.pl b/tests/libtest/mk-lib1521.pl
index 9cd03b37c..b1eaba8d8 100644
--- a/tests/libtest/mk-lib1521.pl
+++ b/tests/libtest/mk-lib1521.pl
@@ -24,9 +24,9 @@
 # Usage:
 # cat ../../include/curl/curl.h | perl mk-lib1521.pl > lib1521.c
 
-# minimum and maximum 32 signed values
-my $minlong = - (1<<31)+1;
-my $maxlong = (1<<31);
+# minimum and maximum long signed values
+my $minlong = "LONG_MIN";
+my $maxlong = "LONG_MAX";
 
 print <<HEADER
 /***************************************************************************
@@ -51,8 +51,8 @@ print <<HEADER
  *
  ***************************************************************************/
 #include "test.h"
-
 #include "memdebug.h"
+#include <limits.h>
 
 /* This source code is generated by mk-lib1521.pl ! */